This project is to investigate the use of an alternative monocrystalline gem (sapphire) to diamond as a cutting edge in electron microscopy (EM). Diagnostic pathology and biomedical research make extensive use of EM. Substituting sapphire knives for diamond knives would reduce the cost of EM by thousands of dollars in each laboratory in the United States. Thin sectioning for EM is done on an ultramicrotone using a knife, the cutting edge of which is usually a diamond. Diamond knives are sharp, long lasting and of uniform duality, but they are expensive ($2,500), fragile and only cut sections of a small area. The major cost of a diamond knife comes from lapping the gem to a molecular edge. Since the knoop hardness value of sapphire is l/3 that of diamond we expect a sapphire edge to be made faster, easier and cheaper. White synthetic sapphire costs approximately $3/gram. Sapphire edges should not be as fragile as diamond because of 1) their greater cleavage resistance and therefore greater impact resistance and 2) the possibility of containing better cutting force distribution. The cutting force will be better distributed by lapping sapphires to a greater included angle. Longer cutting edges can be produced thereby, further reducing the cost/millimeter of cutting edge. We will choose a method of attaching sapphires to steel shanks for lapping. Sapphires will be lapped to a molecular edge using a "low vibration type" air bearing skeif. We have previously made diamond knives in this manner. The lapping characteristics of synthetic white sapphire will be determined, ie speed, duration, angle. Finished edges will be examined by scanning an electron microscopy. Promising edges will be used to thin section for transmission electron microscopy. Thin sectioning characteristics of sapphire will then be determined. The optimal clearance angle (angle to which the edge is lapped) for ultramicrotomy will be found.